Electrical apparatus



Dec. 1, 1942 J. H. CHILES, JR. ET AL 2,303,435

ELECTRICAL APPARATUS Filed Jan. 8, 1941 INVENTORS WITNESSES:

7% v. Wm m W 0%, H B m y @W Patented Dec. 1, 1942 UNITED STATES PATENTOFFICE ELECTRICAL APPARATUS vania Application January 8, 1941, \SerialN0. 373,614

Claims.

Our invention relates to electrical apparatus of the character employinginsulating liquid about an electrical device enclosed in a casingstructure.

In many such electrical apparatus, such, for example, as certain typesof instrument transformers, it is desirable to provide an outer shell orcasing of vitreous insulating material, such as porcelain or glass, forenclosing the electrical device and the insulating liquid in which it isimmersed, which shell or casing performs the joint function of a casingstructure and an insulating bushing. Because of the fragile character ofsuch vitreous insulating material when subjected to severe shocks orblows, it is desirable to provide means independent of the outer casingitself for maintaining the insulating liquid about the electrical devicein case of failure of the outer shell.

It is an object of our invention to provide an electrical apparatusincluding an electrical device within an outer casing and immersed in aninsulating liquid with an auxiliary inner casing or fluid retainer forretaining a major portion of the insulating liquid of the apparatusabout the electrical device in case of failure of the outer shell.

It is a further object of the invention to provide means for sealingthis fluid retainer to the base of the structure to provide aliquid-tight joint between them.

Other objects and advantages of the invention will be apparent from thefollowing description of preferred embodiments thereof, reference beinghad to the accompanying drawing, in which:

Figure 1 is an elevational view, partly in section, illustrating onepreferred embodiment of the invention;

Fig. 2 is an enlarged cross-section of a portion of Fig. 1; and

Figs. 3 and 4 are cross-sectional views of different detailed structuresembodying the invention.

Referring to Fig. 1, a metal base plate I is provided supported upon aframe structure 2, and upon which a cylindrical porcelain or glassmember 3 is mounted to provide an annular wall or 'shell forming theside portion of a casing strucwithin the frame structure 2.

A gasket I0 is provided in an annular recess H in the base plate I,against which the lower end of the cylindrical shell 3 rests, andagainst which it is pressed to make a tight joint by a couplingstructure including an annular ring 12 extending about the lower end ofthe shell and attached thereto by means of cement l3 or other suitablemeans. The ring I2 is provided with an outwardly extending flange I4,against which a pressure ring I5 engages. A series of bolts l6 areprovided extending through openings in the ring 15 and in the outer edgeof the base plate I, and which act through spring members IT to maintaina downward bias on the ring IE to force the shell 3 tightly against thegasket I l. A cover 2! is provided over the upper end of the shell 3,the outer margin of which extends downwardly over a ring 22 which may bescrew-threadedly attached to the upper end of the shell 3 and tightenedto provide a pressure tight seal at 23 between an inner plate member 24and the upper edge of the shell 3. In normal operation of the device, aninsulating liquid is maintained within the shell 3 to a level indicatedby the dash line 25.

An inner insulating liquid retaining shell 26 is provided within theouter shell 3 and spaced therefrom and extending upwardly from the baseplate I to an elevation slightly below that of the liquid level 25. Theinsulating liquid retaining shell 26 should be formed of an insulatingmaterial that is not porous or that will not be easily shattered orbroken. A cylindrical tube of Micarta has been successfully employed asan inner liquid retaining shell. In order to eliminate the highdielectric stresses over the length of the tube and to prevent creepagepaths along the surface of the tube in case of oil leakage from theouter shell, it has been found desirable to provide a considerable spacebetween the top of the tube and the metal parts covering the outer shell3, and particularly to avoid making contact between these parts by thetube 26.

A liquid tight seal is provided between the Micarta tube 26 and thebase'plate I which, in the form of structure shown in Figs. 1 and 2,comprises an upwardly extending metallic flange 21 that is welded to ormade integral with the base plate I. The outer side of the upper edge ofthe flange 21 is cut back from the outer side of the base, and the innerwall of the tube 26 is likewise cut back adjacent the lower end of thetube 26 to provide a recess 28 for accommodating a gasket to effect atight joint between the flange 2'! and the tube 26. The tube 25 ispressed down against the gasket 39 to make a tight seal. The tube isthen maintained in position on the flange by a series of screws 28, oneof which is shown in Figs. 1 and 2.

In Fig. 3, a structure is illustrated for forming a liquid tight jointbetween the liquid retaining tube 25 and the base plate l whichcomprises a flange 3| extending upwardly from the base plate along theinner side of the tube 25 and a recess 32 adjacent the outside of theflange Si, in which a gasket 33 is positioned beneath the lower edge ofthe tube 25. A recess 34 is likewise provided on the outer side of thetube 26 for accommodating a metal ring 35 surrounding the tube. ihe tubeis forced downwardly into tight engagement with the gasket 33 and lockedin place by the ring 35 and a series of screws 35, one of which is shownin Fig. 3.

The structure shown in Fig. 4 diiiers from that shown in Fig. 3essentially in the elimination of the binding ring 35 in the groove 34,together with the screws for maintaining the ring in position, andprovides instead screw-threaded bores 31 on the outer side of the recess32 for accommodating screws 38 which may be tightened into place, andthe lower ends of which engage the tube 26 to maintain it in tightengagement with the gasket 33 positioned in the lower portion of theslot 32 beneath the tube 26.

It will be apparent from the description of the above embodiments of theinvention that should the outer casing wall or shell 3 of the structurebecome chipped or otherwise damaged in such a manner that the insulatingliquid within the apparatus leaks therefrom, the amount of leakage willbe limited to only that above the upper edge of the fluid retaining tube26, and the relatively small portion between the tube 26 and the shell3, so that a substantial quantity of insulating liquid will bemaintained above the electrical d vice 4 to maintain its operatingcharacteristic and prevent the device from becoming inoperative untilsuch time as the apparatus can be repaired.

Modifications in the structure illustrated and described will beapparent to those skilled in the art, and we do not wish to be limitedotherwise than by the scope of the appended claims.

We claim as our invention:

1. In a liquid insulated electrical transformer apparatus, a metal baseplate, a shell of vitreous material mounted thereon and having a liquidtight joint therewith forming a casing wall providing a chamber withinthe shell, a cover for said shell, a core and coil assembly within saidshell, and an insulating liquid within the shell, and a liquid retaineropen at the top and extending upwardly from said base plate within saidshell and about said core and coil assembly to prevent the escape of theliquid from about said core and coil assembly upon failure of saidshell, the top of the liquid retainer terminating below the top level ofthe insulating liquid.

2. In a liquid insulated electrical transformer apparatus, a metal baseplate, a shell of vitreous material mounted thereon and having a liquidtight joint therewith forming a casing wall providing a chamber withinthe shell, a cover for said shell, a core and coil assembly within saidshell, and an insulating liquid within the shell, a cylindrical liquidretainer of tough insulating material open at the top and extendingupwardly from said base plate within said shell and about said core andcoil assembly to prevent the escape of the liquid from about saidapparatus upon failure of said shell, the top of the liquid retainerterminating below the top level of the insulating liquid, and means foreffecting a fluid tight joint between said liquid retainer and saidbase.

3. In a liquid insulated electrical transformer apparatus, a base plate,a shell of vitreous material mounted thereon and forming a liquid tightjoint therewith to provide a chamber extending upwardly from the plate,a liquid retainer comprising a wall of tough insulating material open atthe top and extending upwardly from said base plate within said shelland spaced from said shell, the upper edge of said liquid retainerterminating below the top of said shell, means cooperating with thelower edge of the liquid retainer to form a liquid tight seal betweenthe liquid retainer and said base plate, a core and coil assembly withinsaid shell and liquid retainer, and an insulating liquid within saidshell and liquid retainer to an elevation above the top of said liquidretainer.

4. In a liquid insulated electrical transformer apparatus, a base plate,a shell of vitreous material mounted thereon and forming therewith acasing wall providing a chamber therein, an electrical transformer andan insulating liquid within the chamber to an elevation appreciablybelow the top of the casing wall, a cylindrical liquid retainer of toughinsulating material open at the top and extending upwardly from saidbase plate within said shell and about said electrical transformer toprevent the escape of the liquid from about said transformer uponfailure of said shell, and means for effecting a liquid tight jointbetween said liquid retainer and said base, the upper end of the liquidretainer terminating appreciably below the top level of the insulatingliquid.

5. In a liquid insulated electrical transformer apparatus, a base plate,a shell of vitreous material mounted thereon and forming a casing walloutlining a chamber extending upwardly from the plate, means foreffecting a liquid tight joint between the shell and the base plate, aliquid retainer comprising a wall of tough insulating material open atthe top and extending upwardly from said base plate within said shelland spaced from said shell, the upper edge of said liquid retainerterminating below the top of said shell, means cooperating with thelower edge of the liquid retainer to form a liquid tight seal betweenthe liquid retainer and said base plate, a transformer core and coilassembly within the lower part of the chamber formed by said shell, andinsulating liquid within said shell to a level appreciably below theupper edge of the shell and appreciably above the upper edge of theliquid retainer.

JOHN H. CHILES, Jn. WILLIAM G. McNALLY.

